Abstract: The study of pathogenesis of Mycobacteria infections including MAC has been tremendously aided over the past few years by vastly improved techniques for studying molecular genetics of Mycobacteria. In addition, the mycobacteria genome sequencing projects have made available a large amount of new molecular data as well as cosmid clones containing many genes of importance in pathogenesis. The purpose of this core is to make these advances more readily available to all projects in the Program by providing consolidated facilities for i) DNA sequencing, ii) growth, preparation, cataloging, and storing of vectors for use in mycobacteria transformation, iii) growth, maintenance and storage of normal and mutant mycobacteria strains as they are generated; iv) growth maintenance and storage of DNA clones containing genes of interest; v) growth, maintenance and storage of DNA libraries from MAC strains. The core will employ a single technician to perform these functions and to make these reagents available to all projects in a timely fashion. The core will take advantage of facilities available at Washington University for automated sequencing and for sequence analysis. This core will be instrumental in achieving the objectives of the Program by providing expertise, reagents, and a facility required for the molecular biologic and genetic techniques central to all the projects. In addition, the core will serve an essential role by assuring the quality, maintenance, and distribution of molecular reagents and mycobacteria mutants which will be used by all projects.